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A series of homoleptic Ni bis‐1,1‐dithiolates, [Ni(S2C2RR′)2]2− (R=CN, R′=CN, CO2Et, CONH2, Ph, Ph‐4‐Cl, Ph‐4‐OMe, Ph‐4‐NO2, Ph‐3‐CF3, Ph‐4‐CF3, Ph‐4‐CN; R=NO2, R′=H; R=R′=CO2Et) have been synthesized from the reaction of the alkali metal salt of the ligand and nickel chloride, and isolated as tetraphenylphosphonium or tetrabutylammonium salts. The complexes were characterized by X‐ray crystallography, high‐resolution mass spectrometry, and infrared (IR), nuclear magnetic resonance (NMR) and electronic absorption spectroscopies. The molecular structures show a rigidly square planar Ni(II) center linking two four‐membered chelate rings whose dimensions are constant across the series. The electronic effect of the ligand substituent is revealed in the 13C NMR and electronic spectra, and corroborated by density functional calculations. Electron withdrawing groups deshield the low‐field CS2 resonance, and the signature charge transfer band in the visible region is red‐shifted. These observables have been accurately reproduced computationally, and revealed the Ni contribution to the ground state diminishes with decreasing electron withdrawing capacity of the ligand substituent. In contrast to 1,2‐dithiolates, the redox inactivity afforded by 1,1‐dithiolates stems from the smaller chelate ring and substantially reduced sulfur content that is key to stabilizing the radical form. [ABSTRACT FROM AUTHOR]

New coordination compounds made of two novel tetrazole and C,N‐bipyrazole ligands, 2‐(3,5,5′‐trimethyl‐1′H‐[1,3′‐bipyrazol]‐1′‐yl)acetonitrile (L1), and 1′‐((1H‐tetrazol‐5‐yl)methyl)‐3,5,5′‐trimethyl‐1′H‐1,3′‐bipyrazole (HL2), were prepared and fully characterized by spectroscopic techniques. Their crystal structures were identified by single‐crystal X‐ray diffraction revealing mononuclear complexes: [Ni(L1)3](ClO4)2 (1), [Cd(L1)2Cl2] (2), [Cu(HL2)(L2)]ClO4 (3), [Cu(L2)2] (4) and a dinuclear complex [Co2(HL2)(L2)Cl3] (5) comprising CoII ions in octahedral and tetrahedral surrounding within the same unit. Noticeably, 3 and 4 show different architectural structures due to ligand deprotonation as well as the effect of the counter anion. All compounds demonstrated antimicrobial activity against Gram (+) bacteria Listeria innocua and Staphylococcus aureus, as well as Gram (−) bacteria such as Escherichia coli and Pseudomonas aeruginosa, and antifungal activity against pathogenic fungi Geotrichum candidum, Aspergillus niger, and Penicillium crustosum. Interestingly, a high inhibition activity of 97 % was reached for 5 with a low concentration of only 81.1 μmol/L against Fusarium oxysporum f. sp. Albedinis, which is commonly damaging palm trees crops. [ABSTRACT FROM AUTHOR]

The catalytic efficacy of a novel mononuclear rhenium(I) complex in CO 2 reduction is remarkable, with a turnover number (TON CO ) of 1517 in 3 h, significantly outperforming previous Re(I) catalysts. This complex, synthesized via a substitution reaction on an aromatic ring to form a bromo-bipyridine derivative, L1 = 2-bromo-6-(1 H -pyrazol-1-yl)pyridine, and further reacting with [Re(CO) 5 Cl], results in the facial-tricarbonyl complex [ReL1(CO) 3 Cl] ( 1 ). The light green solid was obtained with an 80% yield and thoroughly characterized using cyclic voltammetry, nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-vis) spectroscopy. Cyclic voltammetry under CO 2 atmosphere revealed three distinct redox processes, suggesting the formation of new electroactive compounds. The studies on photoreduction highlighted the ability of the catalyst to reduce CO 2 , while NMR, FTIR, and electrospray ionization (ESI) mass spectrometry provided insights into the mechanism, revealing the formation of solvent-coordinated complexes and new species under varying conditions. Additionally, computational studies (DFT) were undertaken to better understand the electronic structure and reactivity patterns of 1 , focusing on the role of the ligand, the spectroscopic features, and the redox behavior. This comprehensive approach provides insights into the intricate dynamics of CO 2 photoreduction, showcasing the potential of Re(I) complexes in catalysis.

A series of homoleptic Ni bis-1,1-dithiolates, [Ni(S 2 C 2 RR') 2 ] 2- (R=CN, R'=CN, CO 2 Et, CONH 2 , Ph, Ph-4-Cl, Ph-4-OMe, Ph-4-NO 2 , Ph-3-CF 3 , Ph-4-CF 3 , Ph-4-CN; R=NO 2 , R'=H; R=R'=CO 2 Et) have been synthesized from the reaction of the alkali metal salt of the ligand and nickel chloride, and isolated as tetraphenylphosphonium or tetrabutylammonium salts. The complexes were characterized by X-ray crystallography, high-resolution mass spectrometry, and infrared (IR), nuclear magnetic resonance (NMR) and electronic absorption spectroscopies. The molecular structures show a rigidly square planar Ni(II) center linking two four-membered chelate rings whose dimensions are constant across the series. The electronic effect of the ligand substituent is revealed in the 13 C NMR and electronic spectra, and corroborated by density functional calculations. Electron withdrawing groups deshield the low-field CS 2 resonance, and the signature charge transfer band in the visible region is red-shifted. These observables have been accurately reproduced computationally, and revealed the Ni contribution to the ground state diminishes with decreasing electron withdrawing capacity of the ligand substituent. In contrast to 1,2-dithiolates, the redox inactivity afforded by 1,1-dithiolates stems from the smaller chelate ring and substantially reduced sulfur content that is key to stabilizing the radical form., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The two-electron reductive activation of O 2 to O 2 2- is of particular interest to the scientific community mainly due to the use of peroxides as green oxidants and in powerful fuel cells. Despite of the great importance of vanadium(IV) species to activate the two-electron reductive activation of O 2 , the mechanism is still unclear. Reaction of V IV O 2+ species with the tridentate-planar N,N,N- carboxamide (ΗL) ligands in solution (CH 3 OH:H 2 O) under atmospheric O 2 , at room temperature, resulted in the quick formation of [V V (═O)(η 2 -O 2 )(κ 3 -L)(H 2 O)] and cis -[V V (═O) 2 (κ 3 -L)] compounds. Oxidation of the V IV O 2+ complexes with the sterically hindered tridentate-planar N,N,N- carboxamide ligands by atmospheric O 2 gave only cis -[V V (═O) 2 (κ 3 -L)] compounds. The mechanism of formation of [V V (═O)(η 2 -O 2 )(κ 3 -L)(H 2 O)] (I) and cis -[V V (═O) 2 (κ 3 -L)] (II) complexes vs time, from the interaction of [V IV (═O)(κ 3 -L)(Η 2 Ο) 2 ] + with atmospheric O 2 , was investigated with 51 V, 1 H NMR, UV-vis, cw-X-band EPR, and 18 O 2 labeling IR and resonance Raman spectroscopies revealing the formation of a stable intermediate ( Id ). EPR, MS, and theoretical calculations of the mechanism of the formation of I and II revealed a pathway, through a binuclear [V IV (═O)(κ 3 -L)(H 2 O)(η 1 ,η 1 -O 2 )V IV (═O)(κ 3 -L)(H 2 O)] 2+ intermediate. The results from cw-EPR, 1 H NMR spectroscopies, cyclic voltammetry, and the reactivity of the complexes [V IV (═O)(κ 3 -L)(Η 2 Ο) 2 ] + toward O 2 reduction fit better to an intermediate with a binuclear nature. Dynamic experiments in combination with computational calculations were undertaken to fully elucidate the mechanism of the O 2 reduction to O 2 2- by [V IV (═O)(κ 3 -L)(Η 2 Ο) 2 ] + . The galvanic cell {Zn|V III ,V II || Id , [V IV O(κ 3 -L)(H 2 O) 2 ] + |O 2 |C(s)} was manufactured, demonstrating the important applicability of this new chemistry to Zn|H 2 O 2 fuel cells technology generating H 2 O 2 in situ from the atmospheric O 2 .